This invention relates to a refractory brick segment for use in a heat regenerator or exchanger adapted to be used in a glass fusion industry or an iron and steel industry. In particular, this invention relates to a refractory brick segment having plural grooves and made of an electroformed or electrocast refractory material.
In a conventional glass fusion furnace, many refractory brick segments are assembled in a heat regenerator. Hot exhaust gas is used to heat the refractory brick segments in such a manner that secondary cold combustion air is preheated by the heated brick segments. For example, the hot exhaust gas coming through a blow-off hole of a fusion chamber is usually introduced into an upper end portion of a heat regenerator and then flows out of its lower end portion. While the hot exhaust gas flows downwardly through passages defined by the brick segments, they are heated so as to accumulate heat. Thus, the brick segments gradually increase in temperature. After that, the exhaust gas flow stops by closing a valve, and then secondary air at a room temperature is introduced into a lower portion of the heat regenerator. While the secondary air flows upwardly through the passages of the heat regenerator, the air is heated by the brick segments maintained at a high temperature. Such a cycle of two opposite flows is repeated by switching a valve so that the exhaust gas and the air flow alternately through the heat regenerator.
In order to improve the heat regenerating efficiency of such brick segments, various shapes of them have been proposed so that the heat transmission rate between the refractory brick segment and the hot exhaust gas can be improved.
For example, FIG. 4 shows a conventional refractory brick assembly as disclosed in U.S. Pat. No. 4,436,144 which comprises plural refractory brick segments 1 each made of a refractory material. Each refractory brick segment 1 has a uniform thickness over a full length thereof. The refractory brick segments are vertically piled in such a manner that a plurality of flow passages 2 are formed so as to extend in a vertical direction. Four corners 1a of each refractory brick segment 1 are so cut that a cross section thereof is octagonal. The corners 1a of horizontally adjacent refractory brick segments 1 contact each other while the upper ends 1b contact the corresponding lower ends 1c.
As the thickness of each brick segment is thin in comparison with the conventional post type brick segments, a specific surface area or surface area per unit volume of a regenerator is relatively large. Thus, the thin brick segments have a large heat exchange area for the hot exhaust gas and the secondary air to be heated which flow along the inner and outer walls of the piled brick segments.
FIG. 5 shows another conventional refractory brick assembly for a heat regenerator as disclosed in U.S. Pat. No. 4,974,666 and U.S. Pat. No. 4,874,034 in which each brick segment has a further enlarged specific surface area.
The refractory brick assembly of FIG. 5 includes two types of tube type brick segments 5, 6 each having a plurality of convex and concave strips 5a, 6a in series which extend in parallel to each other on the inner and outer walls of each brick segment. These convex and concave strips 5a, 6a enlarge the specific surface area of the brick segments and produce turbulent flows so as to remarkably increase the heat transmission or exchange rate.
Each brick segment has four corner portions 7 each engaging the corresponding corner portion 7 of a horizontally adjacent segment in such a manner that the convex strips are in contact with the concave strips whereby a large number of brick segments can be piled in a stable condition.
In order to improve corrosion resistance against alkaline dust, electric-fused cast refractory materials have been proposed as materials for refractory brick segments for use in heat regenerators, in place of fired refractory materials. Such electric-fused cast refractory materials are manufactured by electric-fusing desired starting materials and then casting the same by a die means so as to have good thermal stability and dense structure. In particular, the electric-fused cast refractory materials have very excellent corrosion resistance against fused glass or alkaline. The thermal conductivity of the electric-fused cast refractory materials is better than that of the fired refractory materials. Examples of the electric-fused cast refractory materials are alumina-silica-zirconia electric-fused cast refractory materials and zirconia electric-fused cast refractory materials.
The electric-fused cast refractory materials can be easily formed in a complicated shape as they are cast by a mold. However, they are very expensive in comparison with the fired refractory materials.
In order to reduce the production cost, it is effective that the conventional fired refractory materials are used at low-temperature portions and electro-cast refractory materials are used at high-temperature portions. Usually the low-temperature portions of the heat regenerator are positioned in its lower place. If the post-type or tube-type refractory having a thickness of 65 mm or 75 mm is used in its lower place as a heat regenerator brick segment, a high-temperature brick segment having the same thickness as that of a low-temperature brick segment is used in an upper place of the regenerator so as to define the flow passages having the same size as that of the flow passages of the low-temperature brick segments. If a conventional fired refractory brick segment of a tube shape having a rectangular cross-section and a thickness of 40 mm is used in the low-temperature place, an electrocast refractory brick segment having the same thickness as that of the fired refractory brick segment is preferably used in the high-temperature place.